Device for the reduction of nitrogen oxides in the exhaust gas of internal combustion engines

A device for the reduction of nitrogen oxides in the exhaust gas of internal combustion engines has a thermolysis reactor (10). In the thermolysis reactor (10), urea is converted into ammonia and isocyanic acid by means of the supply of heat. In a preferred embodiment of the invention, the thermolysis reactor (10) is arranged within the exhaust gas duct (26) and is thermally coupled to an oxidation catalytic converter (30) which is connected upstream of the thermolysis reactor (10) in the flow direction. As a result of the exothermic reactions taking place in the oxidation catalytic converter (30), it is possible for heating of the thermolysis reactor (10) to take place. In order to further increase the temperature, it is possible for fuel to be injected into the oxidation reactor (30) by means of a fuel supply device. The fuel is burned catalytically in the oxidation catalytic converter (30).